If price is not a problem and your cabinet may get roughed up, go tempered glass. Since most of us have our cabs in our house, I do not expect it will see much abuse I just went with regular glass cut at Lowed for <$5. Tempered glass cannot be cut, it has to be fabricated for you, i.e. you can't just walk into home depot and walk out with a custom cut piece under your arm.
There are different styles of lexan, but I do not think any will look as good as glass.